Various studies have been conducted on displays based on electroluminescent devices to exploit their low power consumption, slimness, and other advantages. Especially, EL displays have been extensively studied because they are easy to decrease in weight and increase in screen size.
Focus of these studies has been upon the development of organic materials which emit light at blue wavelengths, one of the three primary colors, as well as upon the development of organic materials with a capability to transport charges (holes, electrons, etc.). The latter organic materials can possibly be semiconductors or superconductors. The studies have been targeted at both low molecular weight compounds and high molecular weight compounds.
Still, we know only a limited number of organic materials with either excellent color purity and light emitting efficiency or excellent electric charge (carrier) mobility and carrier injection. This challenging issue currently faces our field of study.
Constructing molecules with a highly planar π-conjugated structure is said to be an effective approach to the designing of an organic material with high light emitting efficiency and charge transport capability. A typical, well-known example is given by J. Saltiel, A. Marinari, D. W. L. Chang, J. C. Mitchener, and E. D. Megarity, in J. Am. Chem. Soc., Vol. 101, p. 2982 (1979) and also by J. Saltiel, O. C. Zafiriou, E. D. Megarity, and A. A. Lamola, in J. Am. Chem. Soc., Vol. 90, p. 4759 (1968). Trans-stilbene (see the formula below) in a solution exhibits no higher than a fluorescent quantum yield of 0.05 at room temperature. In contrast, 5,10-dihydroindeno[2,1-a]indene, derived from trans-stilbene by crosslinking its structure with a methylene chain (see the formula below), exhibits a fluorescent quantum yield of close to 1 at room temperature.

We have thought of using a silicon substituent instead of the methylene chain. High light emitting efficiency is obtained with the silicon similarly to the case of the methylene chain. The use of silicon also results in imparting good charge transport capability because of substituent effects of the silicon.
This is because a π-conjugated compound containing silacyclopentadiene (i.e., silole) rings exhibits high electron mobility and acts as a material with an excellent electron transport property. The silole is a silicon analogue of a cyclopentadiene (see the formula above). These facts are well known. See M. Uchida, T. Izumizawa, T. Nakano, S. Yamaguchi, K. Tamao, K. Furukawa, Chem. Mater., Vol. 13, p. 268 (2001).
An example of such a compound is 5,5,10,10-tetramethyl-5,10-disila-5,10-dihydroindeno[2,1-a]indene. The compound is known to be prepared through a reaction shown in formula (I). See M. Serby, S. Ijadi-Maghsoodi, and T. J. Barton, XXXIIIrd Symposium on Organosilicon Chemistry, Abstract No. PA-35, Apr. 6-8, 2000, Saginaw, Mich., USA.

The synthesis of the compound, however, involves special thermal decomposition reactions at high temperatures as will be illustrated later in a reaction formula. The reactions present serious constraints in the synthesis. The reaction is: (i) not suited to mass-volume synthesis, (ii) not suited to the synthesis of derivatives containing functional groups which are essential to the synthesis of polymers, and (iii) not applicable to the synthesis of condensed polycyclic compounds.
To eliminate these serious constraints, we have worked on the development of a synthesis based on a new concept, which has led to the completion of the present invention.